The Humane Society of the United States estimates 6-8 million cats and dogs enter U.S. shelters annually, and approximately 58% of dogs and 46% of cats had not been spayed at the time they were relinquished. A definitive determination as to which animals are spayed or intact has become more difficult with evolving changes in practice, as a visible spay scar is often not apparent when animals are spayed at a very young age or when performed as a laparoscopic ovariectomy. Because the charters for most shelters require documented evidence that an animal has been spayed before they can be adopted out, many dogs and cats require exploratory surgery to determine their spay status. These procedures add costs to the already tight budgets of shelters, and expose many animals to potentially unnecessary surgery.
The presently available, non-surgical means by which presence or absence of the ovaries can be assessed are fraught with difficulties. As mentioned above, the spay scar has become less reliable, and some facilities may perform an exploratory laparatomy on all animals relinquished, because of missed diagnoses when an apparent spay scar was present. Vaginal cytology may be useful, but only if the animal presents during proestrus or estrus, and even then the testing may need to be supplemented by one or more determinations of serum estrogen or progesterone levels. Moreover, the measurement of sex steroids can yield equivocal results depending on the reproductive state of the animal, and more definitive tests that follow stimulation with an injection of gonadotropin releasing hormone (GnRH) are costly and require multiple visits and blood samplings. Similarly, a single measurement of luteinizing hormone (LH) was found not to be a reliable means for determining spay status, and as with sex steroids, GnRH stimulation has been recommended.
As such, a non-surgical diagnostic test is needed to reliably and affordably determine the spay status of shelter animals. Similarly, a better test is needed to assess suspected cases of the ovarian remnant syndrome, as the diagnostic tests presently available have substantial drawbacks. In particular, what is needed is a diagnostic test for a hormone or other factor that is easily and reliably detected in a single sample when the ovaries are present, or undetectable when the ovaries are completely absent.